[
    {
        "year" : "1959",
        "data" : {
            "Яблоки" : 2794966,
            "Грушы" : 3974229,
            "Арбузы" : 762131,
            ...
        }
    },
    {
        "year" : "1970",
        "data" : {
            "Яблоки" : 4238395,
            "Грушы" : 5521917,
            "Арбузы" : 933461,
            ...
        }
    },
    ...
]

{
    labels: ['1959', '1970', ...],
    datasets: [
        {
            label: 'Яблоки',
            data: [2794966, 4238395, ...]
        },
        {
            label: 'Грушы',
            data: [3974229, 5521917, ...]
        },
        {
            label: 'Арбузы',
            data: [762131, 933461, ...]
        },
        ...
    ]
}

var years = [];
var fruits = {};

for(var i=0; i < data.length; i++) {
    years.push(data[i]['year']);

    for(var fruit in data[i]['data']) {
        if(fruits[fruit] == undefined) {
            fruits[fruit] = [];
        }

        fruits[fruit].push(data[i]['data'][fruit]);
    }
}

var data = {};
data['labels'] = years;
data['datasets'] = [];

for(var fruit in fruits) {
    data['datasets'].push({
        'label': fruit,
        'data': fruits[fruit]
    });
}