I don't think there are any foods or meds that strengthen the LES, but there certainly are lots of things that loosen it.
Interesting to note that you suspect (from another of your posts) you got food allergies due to PPIs. I had quite the opposite experience. At least one of my food allergies has lessened dramatically since my fundoplication and getting off PPIs. I have an acquired allergy to sulfites (maybe due to PPIs??? - can't tell after 25 years on them) and now I seem to tolerate foods containing them much better. I won't go as far as to say I'm cured, but my tolerance has increased so that now I can have a small glass of wine occasionally. Now that I don't need PPIs my stomach has normal acidity and I digest things differently.