As this product is a sauce “Faite pour s’étendre” means that it can be spread over whatever it’s used to give taste to; the idea is probably that it is not in the form of a liquid that would run and not stick to the food. A sauce can’t ever be too thick and the problem of cheese that’s difficult to spread because made of too dry a paste is not an inconvenient of that sauce.

There is no doubt that the remote suggestion to sex we can elicit from this “Faite pour s’étendre” will tickle more than one reader, however, not so, I think, without a knowledge of both English and French: “s’étendre” does not have in French the sexual connotations of “lay” and it will take some little bout of conceptualising to extract the idea, which in the end, although it won’t fail to appeal to some — let’s say it again — will appear to the serious-minded rather contrived and far fetched, too foreign to the vernacular (whichever it is); moreover, it is rather a vulgar, gratuitous idea: it amounts to associating sex to everything and anything and on top of that to promoting easy sex as an ideal; as it is an idea that is sufficiently estranged from the context I think it can safely be ignored and there is nothing special in the way of a double meaning; its being insinuated can always be easily dismissed with a remark about not letting one’s imagination run away: it’s simply too much any way one’s looking at it.

There can be a “double entendre” for the word étendre:

• s’étendre (ie , used as a reflexive verb) can mean “to lie down”, eg on a bed
• étendre une sauce means “to spread a sauce*. Hence, in the reflexive form s’étendre: “to be spread”

“Faite pour s’étendre” can then mean both “made to be spread” and “made to go to bed”, the second meaning can then be a (far-fetched and not-so-obvious for native speakers imho…) sexual innuendo.

For the first level, you expect a sauce to be saucy, and for the French counterpart, you expect a spread to bien s’étendre.

If being saucy usually comes along with being clever and entertaining, s’étendre could also be in the same vein. Someone chatty, knowledgeable and entertaining on a certain subject will be able de s’étendre on it, that is, to keep the conversation going for a good little while. Fait(e) pour (anything) is one possible way to express the English born to (something). So fairly similar.

There is however, as mentioned in other answers, a possibility to also understand it as a sexual innuendo, s’étendre from a woman’s perspective also meaning getting herself in the right attitude and position to have sex. Perhaps it wasn’t thought to be entirely inappropriate for a spicy hot sauce (sauce being feminine in French), and indirect enough to escape a kid’s investigation, but opinions vary on the palatability of this kind of slogan, and their potential effects on some important social issues such as “rape culture” might make them inappropriate.