Q.Why do my morning glories wilt in full sun?
For several years I’ve grown them in the ground and in ceramic pots and mulched them well. But in either situation they wilt badly if I don’t water them well every day. They look fine early in the day, but they wilt within an hour after the sun hits them.

Certified GKH Gardening Expert
These will drink water like crazy. It is likely that they are just using all of the water. The soil could be too compact, not letting water through, or too light and not holding enough water for long enough.
This article will give you more information on the care of morning glories: https://www.gardeningknowhow.com/ornamental/vines/morning-glory/growing-morning-glories.htm