Considering the hyperconjucation effects with C-T,C-D and C-H bonds, the maximum efficiency is given by C-H bond.This should mean that C-H must be the weakest bond and must hve the least bond energy compared to others.While all are isotopes of the same element with completely identical outer electronic configuration,then with is the difference in the bond energy?
Heavier isotopes make stronger bonds, therefore C-D and C-T bonds are stronger than C-H bonds. The difference between the bond strengths is however not very significant and can be ignored for most practical purposes.
Therefore, the extent of hyperconjugation can be given as: C-H > C-D > C-T (the difference however is not very significant).
The exact reason for this little difference involves a quantum mechanical explanation, which you should not bother about if you are studying high school chemsitry. If you want to read that, you can refer the links in the comment section.