Scientific evidence remains inconclusive as to whether or not there is a link between the foods that we eat and acne though there is no proven link so far. The reason for acne during periods is very likely hormonal regardless of what you eat during that time. However, it is never a bad idea to eat a balanced diet consisting of fruits, vegetables, whole grains, lean proteins, and healthy fats. Sweets in moderation at any time are fine! If you find that you are eating more sweets during your period than you would like, try to decrease the amount by increasing whole fruits (not fruit juice) which are naturally sweet.