If Fs is sample rate (hear 100 Hz) then the frequency bins are at length(t)/Fs Hz. Since you want your bins spaced 100 Hz apart, you need a longer signal. Try this
Fs=100; %sample rate
t=0:1/Fs:(100-1/Fs); %10,000 samples long
F=[0:length(t)-1]/length(t)*Fs; %where the bins are
y = sin(2*pi*0.33*t)+sin(2*pi*0.23*t)+sin(2*pi*0.1*t);
Y=abs(fft(y))/(length(y)/2); %normalize by the signal length
figure(1);
plot(F,Y)
xlim([0 1]); %zoom in to the part of interest