fprintf('%i %i %i %e \n',G.')
10 0 4 2.701300e-09
10 10 1 7.755000e-09
5 5 2 -1.532230e-08
10 10 3 6.689800e-09
using fprintf. You choose %ifor each integer and %efor each exponent. /ntakes care of line breaks for each line contained in G. Pay attention to G.'; MATLAB is displayed in the main column order, so Gyou must first wrap it.
Even easier, choose format shortGone that automatically executes all the values regardless of their place in the matrix:
format shortG
G =
10 0 4 2.7013e-09
10 10 1 7.755e-09
5 5 2 -1.5322e-08
5 5 2 6.6898e-09