You can always call .data to get a tensor from a variable.
import torch
from torch.autograd import Variable
i = Variable(torch.LongTensor([[0, 1, 1, 2, 2],
                     [2, 0, 2, 1, 0]]))
v = Variable(torch.FloatTensor([3, 4, 5, 1, 2]))
x = Variable(torch.sparse.FloatTensor(i.data, v.data, torch.Size([3,3])))

There is better support for this on master right now, though, if building from source is an option.