I Wash my toddler laundry daily because its smell awful due to dampness and food particle... But I will like to do alternate days because it's more economical... Do you suggest I soak his clothe and wash once every 2 days ?

Prolong soaking also isn't good for the clothes. Maybe those clothes with food particles or dampness set aside and do a quick handwash? whereas clothes isn't too messy can wash every 2-3 days? With clothes being damp and set aside, mold will develop.